1. Field of the Invention
The present invention relates to a pneumatic tire and in more detail, the present invention relates to prevention of bare generation in a side wall region and improvement in appearance quality.
2. Description of the Prior Art
In a pneumatic tire, a side wall forms a smooth curved surface except display of brand names, tire size, and land parts. Since a part which molds said curved surface of a mold is not provided with a concave portion, at the time of vulcanizing and molding a green tire, air is likely to be entrapped between a tire and a mold and further, air is hard to be exhausted. As a result, molding inferiority called bare is likely to be generated in an air entrapped portion.
As one of the countermeasures for preventing bare generation, multiple of air-exhaustion holes called vent holes may be provided with a mold. However, when this method is employed, productivity is lowered since it requires an operation (trimming) in which vent spews that are formed with vent holes are cut after vulcanizing and molding.
In order to solve such a problem, a pneumatic tire is known in which linear projected lines called ridges are provided in the wide range of a side wall (FIGS. 1 to 6 of Japanese Patent Laid-Open Publication No. 8-282215) at an equal interval (for example, not greater than 5 mm).
However, in the above mentioned pneumatic tire, multiple of fine grooves are to be cut on a mold for the formation of a ridge, and there has been a problem of increased production cost of the mold. In addition, since an interval between ridges is small, when dirt is deposited on a side wall, dirt is more elicitable here than other portions, which has also been a problem. Further, since dirt is hard to remove, it has been a problem for users as well.
A side wall is also a portion where joints on which a plurality of rubber members constitute a tire overlap are exposed. In the vicinity joints, as a matter of consequence, subtle concavities and convexities may be formed. For this reason, when linear ridges are regularly arranged, by this subtle concavities and convexities, ridges are deformed, thereby causing a problem of degraded appearance quality.
The object of the present invention lies in prevention of bare generation at the time of vulcanizing and molding, and in improvement in appearance quality by inhibiting the elicitation of concavities and convexities in the vicinity of joints of rubber members on a side wall surface.